DOCSLIB.ORG

Modulation and Detection

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Modulation and Detection Modulation and Detection John Staples, LBNL November 2007 Linear Sum of Two Signals Equation of sinusoidally-varying voltage: V t = V 0 cos 0 t 0 A linear sum of two waves: V t = V 10 cos 1,0 t 1,0 V 20 cos 2,0 t 2,0 No new frequencies are generated. Modulation is a non-linear process that generates additional frequencies. Amplitude Modulation This is a non-linear process, where the amplitude of the signal is modulated by another signal. V t = V 0 1 m cos m t m cos c t c where 0 < m < 1 is the modulation index, um and uc are the carrier and the modulation frequencies. The first term in the parentheses represents the carrier, and the second term the modulation. Using the trig identity 1 cos A cos B = cos A−Bcos AB 2 and ignoring the phases m V t = V 0 cosc t cosm−ct cosmc t [ 2 ] Three frequencies result, the carrier, and two sidebands. The carrier amplitude is unchanged, but the sideband amplitude is directly proportional to the modulation index m. Graphical Representation of an Amplitude Modulated Signal The envelope of the carrier reproduces The spectrum consists of the carrier the modulating waveform. However, and two sidebands, each separated by u from the carrier frequency. the carrier itself is not changing amplitude. c m V t = V 0 cosc t cosm−ct cosmc t [ 2 ] In the frame of the rotating carrier vector, the two sidebands rotate at a frequency of +uc and -uc. Their vector sum (red) represents the envelope of the signal. What would the envelope look like if the carrier were eliminated? Carrier and one sideband? Can an AM signal be overmodulated? Is the modulation information still there? Phase Modulation The instantaneous carrier phase changes with the modulating waveform. V t = V 0 cosc t = V 0 cos c t m cosm t m is the modulation index and um is the modulating frequency. We will use a trig identity to expand this expression: cos AB = cos A cos B − sin A sin B V t = cosc t cosm cosm t − sinc t sinm cosm t V 0 This expression is further expanded with Bessel functions: ∞ k cos z cos = J 0 z 2∑ −1 J 2k z cos2 k k=1 ∞ k sin z cos = 2 ∑ −1 J 2k1 z cos2 k1 k=0 Phase Modulation Spectrum The PM waveform is a double infinite series, with the carrier in quadrature to the nearest sidebands: ∞ V t k = cosc t J 0 m 2∑ −1 J 2 k m cos2 k m t V 0 [ k =1 ] ∞ k sin c t 2∑ −1 J 2 k1 m cos2k 1m t [ k =0 ] The first few terms: V t = J 0 m cosc t V 0 2 J 1 m sin c t cos m t 2 J 2 m cosc t cos2 m t −2 J 3m sin c t cos3m t −2 J 4 m cosc t cos4 m t 2 J 5 m sinc t cos5m t 2 J 6 m cosc t cos6 m t ⋯ Phase Modulation Spectrum Finally, we use another trig identity: 2 sin A cos B = sin AB sin A−B to find 2 cos A cos B = cos AB cos A−B V t = J 0 m cosc t V 0 J 1m [sinc m t sin c − m t ] J 2 m [cosc 2 m t cosc − 2m t ] J 3 m [sin c 3 m t sinc − 3 m t ] J 4 m [cosc 4 m t cosc − 4 m t ] J 5m [sinc 5m t sinc − 5m t ] ⋯ which shows that the sidebands separated by num have an amplitude proportional to Jn(m). Note that each set of sidebands alternates in phase with respect to the carrier Jn(m) Note that a modulation index m = 2.405 that the carrier disappears. This is the first zero of J0(z). At high modulation index, the phase of the sideband reverses. m Graphical Representation of a Frequency Modulated Signal Frequency modulation is a special case of phase modulation, where the phase shift is given by f max = f modulation The spectrum consists of sidebands, spaced by um, with phase dependent on sideband, and amplitude given by the Bessel functions. The envelope is constant, and the frequency varies with the modulation. In the frame of the rotating carrier vector, the sidebands modulate the phase. Here, the carrier amplitude is not constant, but when all sidebands are included, the carrier is constant. Can an FM/PM signal be over- modulated? Demodulation of an Amplitude Modulated Signal The envelope of an Amplitude Modulated signal contains the information. Ways to recover information from an AM signal: 1. Rectify and filter out carrier 2. Synchronously detect (sample) Diode detector rectifies the modulated signal and filters in with the RC integrator. Envelope Demodulation of an Amplitude Modulated Signal The voltage across the RC integrator approximately follows the carrier envelope of the signal. The non-linearity of the diode and the time constant of the integrator may result in some distortion of the recovered modulation. Envelope modulation does not distinguish envelope variations caused by amplitude modulation, or envelope variations caused by, for example, a frequency modulated signal passed through a filter. Synchronous Demodulation of an Amplitude Modulated Signal Synchronous detection multiplies the signal with a carrier of the same frequency as the carrier of the original signal. This way, the phase of the reinserted carrier is significant. m V t = V cos t cos − t cos t × cos t 0[ c 2 m c m c ] c Filter out the components with frequency 2ut: V t 1 m = D t = cos− [ cosm t cos−m t ] V 0 2 4 Synchronous Demodulation 1 m Dt = cos− cos t cos− t 2 4 [ m m ] The recovered information depends on the phase of the reinserted carrier 1 m =0 Dt = cos t In phase: 2 2 m m Quadrature: =/2 Dt = cos −/ 2 −sin t sin t = 0 4 [ m m ] If the reinserted carrier is in phase, the recovered modulation um is recovered, along with a d.c. level. If the reinserted carrier is in quadrature phase, no signal is recovered. Synchronous demodulation is insensitive to noise in quadrature to the reinserted carrier, and also allows two independent signals to be modulated onto one carrier frequency (e.g. color television chroma information). Similar schemes are used for single and double sideband, suppressed-carrier communications system. Logical Phase Detector Circuit Logical diagram: A signal and its inverse are switched to the output at the rate u2+f. The switching wave is call the Local Oscillator (LO). If the switching is in phase with the signal, the average output level integrates to 2/p. If the switching phase is advanced 90 degrees, the output integrates to zero. What if the LO is at 180 degrees? Practical Phase Detector Circuit In the ideal circuit, the local oscillator (LO) performs the switching function. The signal (RF) is chopped, resulting in the Intermediate Frequency (IF) output. LO LO IF IF In the actual circuit, diodes are substituted for the switch, and are RF either saturated in the RF forward bias, or open in the reverse bias case. Actual diodes are not perfect switching devices. They have a current conduction threshold which is temperature dependent. Actual mixers are usually operated with a high LO input level, saturating the diodes, and the IF output may have bias offsets due to mismatch of the diode characteristics. .
Load more

Recommended publications
  • Chapter 1 Experiment-8
    Chapter 1 Experiment-8 1.1 Single Sideband Suppressed Carrier Mod- ulation 1.1.1 Objective This experiment deals with the basic of Single Side Band Suppressed Carrier (SSB SC) modulation, and demodulation techniques for analog commu- nication.− The student will learn the basic concepts of SSB modulation and using the theoretical knowledge of courses. Upon completion of the experi- ment, the student will: *UnderstandSSB modulation and the difference between SSB and DSB modulation * Learn how to construct SSB modulators * Learn how to construct SSB demodulators * Examine the I Q modulator as SSB modulator. * Possess the necessary tools to evaluate and compare the SSB SC modulation to DSB SC and DSB_TC performance of systems. − − 1.1.2 Prelab Exercise 1.Using Matlab or equivalent mathematics software, show graphically the frequency domain of SSB SC modulated signal (see equation-2) . Which of the sign is given for USB− and which for LSB. 1 2 CHAPTER 1. EXPERIMENT-8 2. Draw a block diagram and explain two method to generate SSB SC signal. − 3. Draw a block diagram and explain two method to demodulate SSB SC signal. − 4. According to the shape of the low pass filter (see appendix-1), choose a carrier frequency and modulation frequency in order to implement LSB SSB modulator, with minimun of 30 dB attenuation of the USB component. 1.1.3 Background Theory SSB Modulation DEFINITION: An upper single sideband (USSB) signal has a zero-valued spectrum for f <fcwhere fc, is the carrier frequency. A lower single| | sideband (LSSB) signal has a zero-valued spectrum for f >fc where fc, is the carrier frequency.
    [Show full text]
  • UNIT V- SPREAD SPECTRUM MODULATION Introduction
    UNIT V- SPREAD SPECTRUM MODULATION Introduction: Initially developed for military applications during II world war, that was less sensitive to intentional interference or jamming by third parties. Spread spectrum technology has blossomed into one of the fundamental building blocks in current and next-generation wireless systems. Problem of radio transmission Narrow band can be wiped out due to interference. To disrupt the communication, the adversary needs to do two things, (a) to detect that a transmission is taking place and (b) to transmit a jamming signal which is designed to confuse the receiver. Solution A spread spectrum system is therefore designed to make these tasks as difficult as possible. Firstly, the transmitted signal should be difficult to detect by an adversary/jammer, i.e., the signal should have a low probability of intercept (LPI). Secondly, the signal should be difficult to disturb with a jamming signal, i.e., the transmitted signal should possess an anti-jamming (AJ) property Remedy spread the narrow band signal into a broad band to protect against interference In a digital communication system the primary resources are Bandwidth and Power. The study of digital communication system deals with efficient utilization of these two resources, but there are situations where it is necessary to sacrifice their efficient utilization in order to meet certain other design objectives. For example to provide a form of secure communication (i.e. the transmitted signal is not easily detected or recognized by unwanted listeners) the bandwidth of the transmitted signal is increased in excess of the minimum bandwidth necessary to transmit it.
    [Show full text]
  • CS647: Advanced Topics in Wireless Networks Basics
    CS647: Advanced Topics in Wireless Networks Basics of Wireless Transmission Part II Drs. Baruch Awerbuch & Amitabh Mishra Computer Science Department Johns Hopkins University CS 647 2.1 Antenna Gain For a circular reflector antenna G = η ( π D / λ )2 η = net efficiency (depends on the electric field distribution over the antenna aperture, losses such as ohmic heating , typically 0.55) D = diameter, thus, G = η (π D f /c )2, c = λ f (c is speed of light) Example: Antenna with diameter = 2 m, frequency = 6 GHz, wavelength = 0.05 m G = 39.4 dB Frequency = 14 GHz, same diameter, wavelength = 0.021 m G = 46.9 dB * Higher the frequency, higher the gain for the same size antenna CS 647 2.2 Path Loss (Free-space) Definition of path loss LP : Pt LP = , Pr Path Loss in Free-space: 2 2 Lf =(4π d/λ) = (4π f cd/c ) LPF (dB) = 32.45+ 20log10 fc (MHz) + 20log10 d(km), where fc is the carrier frequency This shows greater the fc, more is the loss. CS 647 2.3 Example of Path Loss (Free-space) Path Loss in Free-space 130 120 fc=150MHz (dB) f f =200MHz 110 c f =400MHz 100 c fc=800MHz 90 fc=1000MHz 80 Path Loss L fc=1500MHz 70 0 5 10 15 20 25 30 Distance d (km) CS 647 2.4 Land Propagation The received signal power: G G P P = t r t r L L is the propagation loss in the channel, i.e., L = LP LS LF Fast fading Slow fading (Shadowing) Path loss CS 647 2.5 Propagation Loss Fast Fading (Short-term fading) Slow Fading (Long-term fading) Signal Strength (dB) Path Loss Distance CS 647 2.6 Path Loss (Land Propagation) Simplest Formula: -α Lp = A d where A and
    [Show full text]
  • Digital Audio Broadcasting : Principles and Applications of Digital Radio
    Digital Audio Broadcasting Principles and Applications of Digital Radio Second Edition Edited by WOLFGANG HOEG Berlin, Germany and THOMAS LAUTERBACH University of Applied Sciences, Nuernberg, Germany Digital Audio Broadcasting Digital Audio Broadcasting Principles and Applications of Digital Radio Second Edition Edited by WOLFGANG HOEG Berlin, Germany and THOMAS LAUTERBACH University of Applied Sciences, Nuernberg, Germany Copyright ß 2003 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England Telephone (þ44) 1243 779777 Email (for orders and customer service enquiries): [email protected] Visit our Home Page on www.wileyeurope.com or www.wiley.com All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except under the terms of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London W1T 4LP, UK, without the permission in writing of the Publisher. Requests to the Publisher should be addressed to the Permissions Department, John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England, or emailed to [email protected], or faxed to (þ44) 1243 770571. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the Publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought.
    [Show full text]
  • Lecture 25 Demodulation and the Superheterodyne Receiver EE445-10
    EE447 Lecture 6 Lecture 25 Demodulation and the Superheterodyne Receiver EE445-10 HW7;5-4,5-7,5-13a-d,5-23,5-31 Due next Monday, 29th 1 Figure 4–29 Superheterodyne receiver. m(t) 2 Couch, Digital and Analog Communication Systems, Seventh Edition ©2007 Pearson Education, Inc. All rights reserved. 0-13-142492-0 1 EE447 Lecture 6 Synchronous Demodulation s(t) LPF m(t) 2Cos(2πfct) •Only method for DSB-SC, USB-SC, LSB-SC •AM with carrier •Envelope Detection – Input SNR >~10 dB required •Synchronous Detection – (no threshold effect) •Note the 2 on the LO normalizes the output amplitude 3 Figure 4–24 PLL used for coherent detection of AM. 4 Couch, Digital and Analog Communication Systems, Seventh Edition ©2007 Pearson Education, Inc. All rights reserved. 0-13-142492-0 2 EE447 Lecture 6 Envelope Detector C • Ac • (1+ a • m(t)) Where C is a constant C • Ac • a • m(t)) 5 Envelope Detector Distortion Hi Frequency m(t) Slope overload IF Frequency Present in Output signal 6 3 EE447 Lecture 6 Superheterodyne Receiver EE445-09 7 8 4 EE447 Lecture 6 9 Super-Heterodyne AM Receiver 10 5 EE447 Lecture 6 Super-Heterodyne AM Receiver 11 RF Filter • Provides Image Rejection fimage=fLO+fif • Reduces amplitude of interfering signals far from the carrier frequency • Reduces the amount of LO signal that radiates from the Antenna stop 2/22 12 6 EE447 Lecture 6 Figure 4–30 Spectra of signals and transfer function of an RF amplifier in a superheterodyne receiver. 13 Couch, Digital and Analog Communication Systems, Seventh Edition ©2007 Pearson Education, Inc.
    [Show full text]
  • Demodulation of Chaos Phase Modulation Spread Spectrum Signals Using Machine Learning Methods and Its Evaluation for Underwater Acoustic Communication
    sensors Article Demodulation of Chaos Phase Modulation Spread Spectrum Signals Using Machine Learning Methods and Its Evaluation for Underwater Acoustic Communication Chao Li 1,2,*, Franck Marzani 3 and Fan Yang 3 1 State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China 2 University of Chinese Academy of Sciences, Beijing 100190, China 3 LE2I EA7508, Université Bourgogne Franche-Comté, 21078 Dijon, France; [email protected] (F.M.); [email protected] (F.Y.) * Correspondence: [email protected] Received: 25 September 2018; Accepted: 28 November 2018; Published: 1 December 2018 Abstract: The chaos phase modulation sequences consist of complex sequences with a constant envelope, which has recently been used for direct-sequence spread spectrum underwater acoustic communication. It is considered an ideal spreading code for its benefits in terms of large code resource quantity, nice correlation characteristics and high security. However, demodulating this underwater communication signal is a challenging job due to complex underwater environments. This paper addresses this problem as a target classification task and conceives a machine learning-based demodulation scheme. The proposed solution is implemented and optimized on a multi-core center processing unit (CPU) platform, then evaluated with replay simulation datasets. In the experiments, time variation, multi-path effect, propagation loss and random noise were considered as distortions. According to the results, compared to the reference algorithms, our method has greater reliability with better temporal efficiency performance. Keywords: underwater acoustic communication; direct sequence spread spectrum; chaos phase modulation sequence; partial least square regression; machine learning 1. Introduction The underwater acoustic communication has always been a crucial research topic [1–6].
    [Show full text]
  • AM Demodulation(Peak Detect.)
    AM Demodulation (peak detect.) Demodulation is about recovering the original signal--Crystal Radio Example Antenna = Long WireFM AM A simple Diode! (envelop of AM Signal) Tuning Demodulation Filter Circuit Circuit (Mechanical) Basically a “tapped” Inductor (L) and variable Capacitor (C) We’ll not spend a lot of time on the AM “crystal radio”, although I love it dearly as a COOL, ultra-minimal piece of electronics-- Imagine, you get radio FREE with no batteries required. But… The things we will look at and actually do a bit in lab is to consider the “peak detector” (I.e. the means for demodulating the AM signal) From a block diagram point of view, the circuit has a tuning component (frequency selective filter) attached to the antenna (basically a wire for the basic X-tal radio). The demodulation consists of a diode (called the “crystal” from the good old days of “Empire of the Air”…movie we’ll watch) and an R-C filter to get rid of the carrier frequency. In the Radio Shack version there is no “C” needed; your ear bones can’t respond to the carrier so they act as “the filter”. The following slide gives a more electronics-oriented view of the circuit… 1 Signal Flow in Crystal Radio-- +V Circuit Level Issues Wire=Antenna -V time Filter: BW •fo set by LC •BW set by RLC fo music “tuning” ground=0V time “KX” “KY” “KZ” frequency +V (only) So, here’s the incoming (modulated) signal and the parallel L-C (so-called “tank” circuit) that is hopefully selective enough (having a high enough “Q”--a term that you’ll soon come to know and love) that “tunes” the radio to the desired frequency.
    [Show full text]
  • En 300 720 V2.1.0 (2015-12)
    Draft ETSI EN 300 720 V2.1.0 (2015-12) HARMONISED EUROPEAN STANDARD Ultra-High Frequency (UHF) on-board vessels communications systems and equipment; Harmonised Standard covering the essential requirements of article 3.2 of the Directive 2014/53/EU 2 Draft ETSI EN 300 720 V2.1.0 (2015-12) Reference REN/ERM-TG26-136 Keywords Harmonised Standard, maritime, radio, UHF ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N° 348 623 562 00017 - NAF 742 C Association à but non lucratif enregistrée à la Sous-Préfecture de Grasse (06) N° 7803/88 Important notice The present document can be downloaded from: http://www.etsi.org/standards-search The present document may be made available in electronic versions and/or in print. The content of any electronic and/or print versions of the present document shall not be modified without the prior written authorization of ETSI. In case of any existing or perceived difference in contents between such versions and/or in print, the only prevailing document is the print of the Portable Document Format (PDF) version kept on a specific network drive within ETSI Secretariat. Users of the present document should be aware that the document may be subject to revision or change of status. Information on the current status of this and other ETSI documents is available at http://portal.etsi.org/tb/status/status.asp If you find errors in the present document, please send your comment to one of the following services: https://portal.etsi.org/People/CommiteeSupportStaff.aspx Copyright Notification No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm except as authorized by written permission of ETSI.
    [Show full text]
  • Of Single Sideband Demodulation by Richard Lyons
    Understanding the 'Phasing Method' of Single Sideband Demodulation by Richard Lyons There are four ways to demodulate a transmitted single sideband (SSB) signal. Those four methods are: • synchronous detection, • phasing method, • Weaver method, and • filtering method. Here we review synchronous detection in preparation for explaining, in detail, how the phasing method works. This blog contains lots of preliminary information, so if you're already familiar with SSB signals you might want to scroll down to the 'SSB DEMODULATION BY SYNCHRONOUS DETECTION' section. BACKGROUND I was recently involved in trying to understand the operation of a discrete SSB demodulation system that was being proposed to replace an older analog SSB demodulation system. Having never built an SSB system, I wanted to understand how the "phasing method" of SSB demodulation works. However, in searching the Internet for tutorial SSB demodulation information I was shocked at how little information was available. The web's wikipedia 'single-sideband modulation' gives the mathematical details of SSB generation [1]. But SSB demodulation information at that web site was terribly sparse. In my Internet searching, I found the SSB information available on the net to be either badly confusing in its notation or downright ambiguous. That web- based material showed SSB demodulation block diagrams, but they didn't show spectra at various stages in the diagrams to help me understand the details of the processing. A typical example of what was frustrating me about the web-based SSB information is given in the analog SSB generation network shown in Figure 1. x(t) cos(ωct) + 90o 90o y(t) – sin(ωct) Meant to Is this sin(ω t) represent the c Hilbert or –sin(ωct) Transformer.
    [Show full text]
  • Continuous Phase Modulation with Faster-Than-Nyquist Signaling for Channels with 1-Bit Quantization and Oversampling at the Receiver Rodrigo R
    1 Continuous Phase Modulation With Faster-than-Nyquist Signaling for Channels With 1-bit Quantization and Oversampling at the Receiver Rodrigo R. M. de Alencar, Student Member, IEEE, and Lukas T. N. Landau, Member, IEEE, Abstract—Continuous phase modulation (CPM) with 1-bit construction of zero-crossings. The proposed CPM waveform quantization at the receiver is promising in terms of energy conveys the same information per time interval as the common and spectral efficiency. In this study, CPM waveforms with CPFSK while its bandwidth can be the same and even lower. symbol durations significantly shorter than the inverse of the signal bandwidth are proposed, termed faster-than-Nyquist CPM. Referring to the high signaling rate, like it is typical for faster- This configuration provides a better steering of zero-crossings than-Nyquist signaling [9], the novel waveform is termed as compared to conventional CPM. Numerical results confirm a faster-than-Nyquist continuous phase modulation (FTN-CPM). superior performance in terms of BER in comparison with state- Numerical results confirm that the proposed waveform yields of-the-art methods, while having the same spectral efficiency and a significantly reduced bit error rate (BER) as compared to a lower oversampling factor. Moreover, the new waveform can be detected with low-complexity, which yields almost the same the existing methods [7], [6] with at least the same spectral performance as using the BCJR algorithm. efficiency. In addition, FTN-CPM can be detected with low- complexity and with a lower effective oversampling factor in Index Terms—1-bit quantization, oversampling, continuous phase modulation, faster-than-Nyquist signaling.
    [Show full text]
  • Energy-Detecting Receivers for Wake-Up Radio Applications
    Energy-Detecting Receivers for Wake-Up Radio Applications Vivek Mangal Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy under the Executive Committee of the Graduate School of Arts and Sciences COLUMBIA UNIVERSITY 2020 © 2019 Vivek Mangal All Rights Reserved Abstract Energy-Detecting Receivers for Wake-Up Radio Applications Vivek Mangal In an energy-limited wireless sensor node application, the main transceiver for communication has to operate in deep sleep mode when inactive to prolong the node battery lifetime. Wake-up is among the most efficient scheme which uses an always ON low-power receiver called the wake-up receiver to turn ON the main receiver when required. Energy-detecting receivers are the best fit for such low power operations. This thesis discusses the energy-detecting receiver design; challenges; techniques to enhance sensitivity, selectivity; and multi-access operation. Self-mixers instead of the conventional envelope detectors are proposed and proved to be op- timal for signal detection in these energy-detection receivers. A fully integrated wake-up receiver using the self-mixer in 65 nm LP CMOS technology has a sensitivity of −79.1 dBm at 434 MHz. With scaling, time-encoded signal processing leveraging switching speeds have become attractive. Baseband circuits employing time-encoded matched filter and comparator with DC offset compen- sation loop are used to operate the receiver at 420 pW power. Another prototype at 1.016 GHz is sensitive to −74 dBm signal while consuming 470 pW. The proposed architecture has 8 dB better sensitivity at 10 dB lower power consumption across receiver prototypes.
    [Show full text]
  • FM Stereo Format 1
    A brief history • 1931 – Alan Blumlein, working for EMI in London patents the stereo recording technique, using a figure-eight miking arrangement. • 1933 – Armstrong demonstrates FM transmission to RCA • 1935 – Armstrong begins 50kW experimental FM station at Alpine, NJ • 1939 – GE inaugurates FM broadcasting in Schenectady, NY – TV demonstrations held at World’s Fair in New York and Golden Gate Interna- tional Exhibition in San Francisco – Roosevelt becomes first U.S. president to give a speech on television – DuMont company begins producing television sets for consumers • 1942 – Digital computer conceived • 1945 – FM broadcast band moved to 88-108MHz • 1947 – First taped US radio network program airs, featuring Bing Crosby – 3M introduces Scotch 100 audio tape – Transistor effect demonstrated at Bell Labs • 1950 – Stereo tape recorder, Magnecord 1250, introduced • 1953 – Wireless microphone demonstrated – AM transmitter remote control authorized by FCC – 405-line color system developed by CBS with ”crispening circuits” to improve apparent picture resolution 1 – FCC reverses its decision to approve the CBS color system, deciding instead to authorize use of the color-compatible system developed by NTSC – Color TV broadcasting begins • 1955 – Computer hard disk introduced • 1957 – Laser developed • 1959 – National Stereophonic Radio Committee formed to decide on an FM stereo system • 1960 – Stereo FM tests conducted over KDKA-FM Pittsburgh • 1961 – Great Rose Bowl Hoax University of Washington vs. Minnesota (17-7) – Chevrolet Impala ‘Super Sport’ Convertible with 409 cubic inch V8 built – FM stereo transmission system approved by FCC – First live televised presidential news conference (John Kennedy) • 1962 – Philips introduces audio cassette tape player – The Beatles release their first UK single Love Me Do/P.S.
    [Show full text]